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Re: 71 GMC Longhorn, compatible engine and transmition
Quote:
Originally Posted by davischevy
The turbo 400 transmission will not shift without vacuum from the intake manifold to the modulator valve. You should check the vacuum lines before you assume the transmission is bad.
A vacuum leak will also cause a rough idle.
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I was thinking maybe the modulator, but yeah, this is another check. Though if a 400 never goes into 3rd, there is another failure mode, but I forget what it is.
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~Steven
'70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper
Simi Valley, CA
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